1. Field of the Invention
The present invention generally relates to a control system for an engine of a marine propulsion system and, more particularly, to a control system that improves the shifting process from neutral into either forward or reverse gear so that the impact of the shift event is minimized and the likelihood of stalling is decreased.
2. Description of the Prior Art
It is very well known to those skilled in the art of marine propulsion systems that shifting from one gear position to another can result in significant impact noise and impact shock to the drive unit. It is also well known to those skilled in the art that one method for alleviating these problems is to deprive one or more cylinders of the engine from an ignition spark during the shift event. This has the effect of slowing the operating speed of the engine and decreasing the torque provided by the engine to the drive train.
U.S. Pat. Re. 32,998, which issued to Davis on Jul. 25, 1989, discloses an ignition interrupt system with a stall interval. The spark ignition interrupt system is provided for a marine propulsion internal combustion engine to reduce engine speed and facilitate shifting of a marine propulsion transmission. Spark ignition is terminated in response to a given shift condition until engine speed drops below a given cut-in speed or until completion of the shifting, whichever occurs first. A stall interval is also started in response to the given shift condition. The engine is stalled upon completion of the stall interval if the shifting is not complete, even if engine speed has dropped below the given cut-in speed.
U.S. Pat. No. 5,853,306, which issued to Worth et al. on Dec. 29, 1998, describes an operation of marine engines. It discloses a method of operation of a marine engine which comprises sensing an operator demand for a gear-shift and, in response to the sensing of the operator command, varying the engine torque profile to enable the gear-shift. Typically, the engine torque profile is required to be varied to overcome forces resistive to gear-shift.
U.S. Pat. No. 4,262,622, which issued to Dretzka et al. on Apr. 21, 1981, describes a marine propulsion device including ignition interruption means to assist transmission shifting. The device and apparatus and methods are disclosed for assisting transmission shifting. The marine propulsion device includes an internal combustion engine and a reversing transmission having a pair of bevel gears and a clutch dog moveable between a neutral position out of engagement with the bevel gears and forward and reverse drive positions in full engagement with one of the bevel gears. The marine propulsion device also includes a shift assistance arrangement included in a shift mechanism for axially moving the clutch dog between the neutral and drive positions, and which includes a load sensing lost motion shift lever arrangement having a first switch which is actuated when the resistance to axially moving the clutch dog into a drive position exceeds an upper limit. The shift assistance arrangement also includes an ignition interruption circuit responsive to actuation of the first switch for selectively interrupting the ignition of the internal combustion engine to reduce the engine torque transmitted to the bevel gears to effect relative angular displacement of the clutch dog and the bevel gears to thereby assist the shift mechanism in moving the clutch dog into and out of a drive position.
U.S. Pat. No. 6,470,852, which issued to Kanno on Oct. 29, 2002, describes an engine control system that includes an improved construction that can release an engine from an abnormal engine speed so that, for example, the operator can operate a shift actuator without any overload. The engine includes an air induction system that introduces air to the combustion chamber and includes a throttle valve. The throttle valve admits the air to flow through the air induction system unless placed in a closed position. The throttle valve position sensor is arranged to sense the position of the throttle valve. In one operating mode, the slowdown control is made when the throttle position signal indicates that the throttle valve is generally at the closed position and the speed signal indicates that the engine speed exceeds a preset speed.
U.S. Pat. No. 5,692,992 which issued to Arvidsson et al. on Dec. 2, 1997, describes a shift assist and engine interrupter apparatus. The shift assist apparatus for a marine drive includes a tube having a pair of biased springs, between which a sleeve at the end of a transmission cable is moveably retained. A remote control cable is fixedly attached to the tube. High transmission cable shift forces associated with resistance to shifting cause the sleeve to move against the bias of one of the springs. A sensor detects this movement and sends an electrical signal to interrupt the engine ignition circuit, thereby preventing the firing of one or more cylinders of the engine.
U.S. Pat. No. 5,403,246, which issued to Umemoto on Apr. 4, 1995, describes a control device for an internal combustion engine. The device comprises a shift lever position detector for detecting a shift lever position of an engine for an outboard motor and an ignition timing controller for retarding an ignition timing of the engine for the outboard motor based on the shift lever position when a clutch is disengaged.
U.S. Pat. No. 5,827,150, which issued to Mukumoto on Oct. 27, 1998, describes an engine control having shift assist with fuel injected during ignition cutoff while shifting. The system includes an arrangement for slowing the speed of the engine by disabling certain cylinders in the event of an abnormal engine running condition. Also, an arrangement is provided for slowing the speed of the engine if a change speed transmission for driving the propulsion shaft by the engine offers more than a predetermined resistance to shifting. The controls are interrelated so that the engine protection control predominates. That is, if the engine is in protection control mode and the operator attempts a shift and more than a predetermined resistance is felt, the shift control routine will not be initiated to effect any additional engine speed reduction.
U.S. Pat. No. 4,843,914, which issued to Koike on Jul. 4, 1989, describes a shift assisting device for a marine propulsion unit. Several embodiments of shift assisting devices for marine propulsion units are described, wherein the torque of the engine is reduced if there is resistance to shifting by reducing the amount of fuel supply to the engine. Embodiments are depicted and described wherein this is done by throttling the intake charge or reducing the supply of fuel supplied by a fuel injection nozzle and the principle is applied to either spark ignited or diesel engines.
U.S. Pat. No. 4,938,189, which issued to Morita et al. on Jul. 3, 1990, describes an automatic ignition control system which comprises an ignition circuit of capacitor charge-discharge type. The ignition timing is determined by controlling the charge-discharge cycle of a capacitor by an output signal from an engine speed detection circuit. An overspeed control circuit stops the ignition when a detection output signal of the engine speed detection circuit exceeds a reference voltage level corresponding to a set engine speed. A slowing down control circuit is actuated in response to an engine slowing down operation start switch for realizing a hypothetical condition substantially equivalent to the one in which the engine speed detection circuit detects an engine speed higher than the actual engine speed thereby to accomplish engine slowing down operation by increasing the reference voltage level gradually or increasing the output signal level of the engine speed detection circuit stepwise.
U.S. patent application Ser. No. 09/997,124 which was filed on Nov. 28, 2001, describes a shift assist system for an outboard motor. The system regulates the torque of the engine to ensure proper effortless shifting. The system recognizes open circuit or short circuit faults and nevertheless enables the torque of the engine to be reduced to facilitate easy gear selection.
U.S. Pat. No. 6,647,956, which issued to Sharpton on Nov. 18, 2003, discloses a sound attenuating system for a marine engine. A sound attenuator is provided for an idle air control valve system in order to reduce noise emanating from the idle air control valve. The sound attenuator comprises a fibrous pad that is inserted into an air conduit of the idle air control system. In a preferred embodiment, the fibrous pad is inserted into the air conduit near the air inlet where the conduit receives air from a region upstream, or above the throttle plate. A small hole can be provided through the air inlet. In certain embodiments, the air inlet of the air conduit is an opening formed in an inner cylindrical surface of the throttle body. In alternative embodiments, the air inlet can be remote from the internal surface of the throttle body.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a marine propulsion system could be provided with an engine control system that controls the idle speed of the engine, prior to an imminent shift event from neutral to either forward or reverse gear, in such a way that the idle speed is slowed in most conditions to minimize the impact of an engagement of the clutch. Whether the clutch is a cone clutch or a dog clutch, proper control of the idle speed will minimize the impact shock and noise associated with a shifting event from neutral to either forward or reverse gear positions. The idle speed can be decreased or increased in anticipation of a shift event, depending on whether the marine vessel is stationary or in the process of being rapidly shifted from forward to reverse or vice versa.